Fig. 1. GP cell migration in optic nerves in in vivo or in vitro cultures together with the optic chiasma and/or the eyeball. Migrating cells exiting from the UV-irradiated area were observed when the optic nerve was cultured with the optic chiasma. (A) schematic diagram showing the principle of the UV-TD labeling method used to study cell migration. The UV-irradiated site was identified by TD-positive stationary cells (see Tamamaki et al., 1999 or the text for details). (B) TD-labeled cells observed in a paraffin section of an optic nerve fixed immediately after UV irradiation. (C) TD-labeled cells observed in an optic nerve fixed after culture for five hours. (D) TD-labeled cells in an optic nerve cultured with the optic chiasma and eyeball for five hours. (E-G) reconstructed UV-irradiated area. Photographs of serial sections were taken on transparent paper and they were overlapped to confirm the UV-irradiation area. (H-I) Reconstructed pattern of the TD-labeled nuclei distribution shown in C and D. The labeled migrating cells (red dots) were traced onto the transparent photographs, which were then overlapped to show the distribution of the labeled migrating cells. Arrows in C, F and H, and D, G and I indicate the same cells. Arrowheads indicate the UV-irradiated area, as estimated from the distribution of TD-labeled stationary cells. (J) NG2-negative immunoreactive cells in the newborn rat optic nerve. (K) Double staining study for TD and NG2 immunoreactivity. The rectangular area in the figure was enlarged in L. (L) NG2-positive migrating cells (single arrows) and NG2-negative migrating cells (double arrows). (M) An optic nerve cultured with an eyeball and the chiasma in vitro. (N) Schematic diagrams summarizing the condition under which the GP cell migration was observed. The optic chiasma was necessary to guide the GP cell migration distally. Scale bar in B, 100 µm (B-I); in K is 100 µm; in J and L are 10 µm.
